Hoist



March 15, 1966 G. BOULSOVER HOIST 5 Sheets-Sheet 1 Filed Sept. 2, 1964March 15, 1966 G. BOULSOVER 3,240,529

nozsw Filed Sept. 2, 1964 5 Sheets-Sheet 2 f/, i i- March 15, .1966 G.BOULSOVER HOIST 5 Sheets-Sheet 3 Filed Sept. 2, 1964 March 15, 1966 s.BOULSOVER 3,240,529

HOIS'I' Filed Sept. 2, 1964 5 Sheets-Sheet 4.

March 15, 1966 G. BOULSOVER 5 Sheets-Sheet 5 Filed Sept. 2, 1964 UnitedStates Patent 3,240,529 HOIST Geoffrey Boulsover, London, England,assignor to The Amalgamated Dental Company Limited, London, England, aBritish company Filed Sept. 2, 1964, Ser. No. 393,930 1 Claim. (Cl.297-327) This invention relates to supports for the body which areadjustable in height and furnished with ram mechanism for effecting thevertical movement. The most usual examples are dental chairs.

In my Patent No. 927,600 I have already described an arrangement of bodysupport, comprising a base, a body support member such as a dentalchair, and a lazy tongs mechanism holding these apart, the base alsocarrying a hydraulic ram mechanism linked to a centre line pivot of thelazy tongs mechanism whereby the vertical movement of the body supportmember may be amplified with respect to the movement of the rammechanism. The ram mechanism on the other hand may incorporate an oilreservoir together with means for pressurising the air in the spaceabove the oil, there being an operator controlled first Valve forregulating the air pressure in the oil reservoir and a second valve forisolating hydraulic fluid in the ram from the oil in the reservoir atany desired elevation of the hoist. This use of pressurised air providesfor a particularly smooth operation of the hydraulic ram and avoids theneed for a separate pump taking into account the fact that modern dentalunits and other locations where the body support of the invention willbe situated, almost invariably are furnished with a source or supply ofcompressed air. The second valve just referred to enables the ram to belocked at any desired elevation and may be arranged to closeautomatically when the first valve, for the pressurised air, isreleased.

The present invention is concerned with an additional, tilting movementof the body support and has as one object to provide means whereby thebody support may be tilted forwardly or backwardly under power exertedby a hydraulic ram. Another object of the invention is to providehydraulic and pneumatic circuitry whereby the body support may be raisedor lowered and simultaneously may be tilted in a forward or reversedirection. Yet another object is to provide hydraulic and pneumaticcircuitry whereby the raising and lowering of the body support may beaccomplished by oil pressurised by compressed air, whilst the tilting ofthe body support is likewise accomplished by oil pressurised bycompressed air from the same source whilst maintaining the respectivepneumatic circuitries isolated from one another. In another aspect, itis an object of the invention to provide means whereby the shape of thebody support may be varied automatically as the body support is tilted,to conform with a more natural or more comfortable position of theseated body.

In one aspect the invention consists in a body support comprising a basecarrying a vertically extendable body support member and a firsthydraulic ram mechanism for raising and lowering the body supportmember, this first hydraulic mechanism comprising a first hydraulic ramand an associated first oil reservoir with respective hydrauliccircuitry and with an associated pneumatic circuitry incorporating anoperator controlled first valve for pressurising the oil reservoir, thebody support member being tiltably mounted and connected with a secondhydraulic mechanism incorporating a respective second hydraulic,double-acting ram, each side of which is connected by hydrauliccircuitry to a respective second and third oil reservoir associated withsecond pneumatic circuitry incorporating second and third operatorcontrolled pneumatic valve arrangements for pressurising the second andthird oil reservoirs and exhausting air from the third and second oilreservoirs respectively, the hydraulic circuitry of each hydraulic rammechanism incorporating a respective control valve associated with meansfor closing this control valve to lock the respective hydraulic ram inunison with release of the respective operator-controlled valve.

Preferably, the first hydraulic ram for raising and lowering the hoist,hereinafter referred to as the lifting ram, and the second hydraulic ramfor tilting the support table or chair, hereinafter referred to as thetilting ram, have respective pneumatically operated valves forregulating the supply of compressed air to their respective oilreservoirs and for regulating the movement of the respective hydraulicfluid, these being the operator-controlled valves just referred to.These pneumatically operated valves may in turn be associated withpneumatic pilot valves grouped together to represent a portable controlbox linked by flexible piping to the remainder of the hoist, but mayadditionally or alternatively be operated directly by a foot control.Generally, four pilot valves will be thus provided, the actuation of oneaffording a forward tilt response from the tilting ram, actuation of thenext affording a rearward tilt response, actuation of a third affordinghoist lift whilst actuation of the fourth affords hoist lowering. Thefoot control may be furnished with plunger devices as an alternativemeans for actuating the pneumatically operated valves remotely, by meansof a flexible hydraulic linkage leading to, for example, a hydraulicbellows for manual operation.

Broadly, the invention therefore provides hydraulic rams and pneumaticcircuitry and hydraulic circuitry whereby a lifting ram may be actuatedto raise or lower a body support under the influence of thrust derivedfrom compressed air, the position heightwise of the body support beinglocked by a hydraulic valve which comes into operation automatically asthe operator-control is released, whilst functioning independently ofthis, there is a tilting ram for tilting the body support forwardly orbackwardly likewise associated with a hydraulic locking valve. Twoseparate oil reservoirs are provided for each side of the double-actingtilting ram and either side can be pressurised simultaneously withpressure release on the other side for immediate tilting action.Generally, the operatorcontrol valve for the lifting ram circuitry andthe operatorcontrol valve for the tilting ram circuitry are each doubledone valve of each pair serving for initiating movement in one directionand the other for initiating movement in the reverse direction. Thegeneral arrangement permits the tilt to be reversed, immediately orafter a delay, as soon as the respective control valve is operated andwithout having to rely upon a powerful return spring.

In addition to the valves which have already been enumerated, a valve orvalves may be incorporated, suitably operated by being tripped, tocontrol the maximum movement of the lifting and/or tilting rams in oneor both directions. Thus, a maximum lift trip valve may be arranged tobe tripped automatically when the hoist reaches a certain height therebyfor example cancelling the actuation of the lift pilot valve for thelifting ram.

To provide an enhanced degree of comfort and security in a chair typebody support, the support in accordance with a further feature of theinvention comprises a seat portion which is pivotally mounted inrelation to the re mainder of the support and associated with a cam orstop arranged to tilt this seat portion differentially as the support asa whole is tilted so that the seat portion assumes a more acute anglewith a chair back portion and more obtuse angle with a chair leg portionas the body support as a whole is tilted towards an upright position.The chair type body support in this case preferably has a band offiexible upholstery overlying the seat portion so that the change inangle is transmitted through this upholstery. In the preferred andsimplest arrangement, the relative tilting of the chair seat portion isaccomplished by hinging this rearwardly and providing a stop below amore forward part of the seat portion so that as the chair as a wholetilts forwardly, the seat portion engages this stop and is held at apredetermined inclination to the horizontal whilst the remainder of thechair continues to swing forwardly. Other mechanical arrangements couldof course readily be contrived, all serving the common purpose ofconverting a relatively fiat S-shape to a relatively acute S-shape beingmore appropriate to a reclining position and an upright positionrespectively.

The invention will be described further with reference to theaccompanying drawings, of which:

FIGURE 1 is a side sectional view of the base portion of a dental chair,

FIGURE 2 is a part sectional plan view corresponding to FIGURE 1,

FIGURE 3 is a side view of the upper portion of the dental chair,

FIGURE 4 is a front view corresponding to FIGURE 3, and

FIGURE 5 is a hydraulic/ pneumatic circuit diagram.

As shown in FIGURES l and 2, the lower portion of the dental chairassembly comprises a base 1 for standing on the floor supporting alifting ram 2. The base also supports a lazy tongs or trellis mechanism3, the upper end 4 of which carries a platform 5 on which is carried theseat illustrated in FIGURES 3 and 4 described hereinafter. The platform5 also carries a skirt 6 which shields the lazy tongs and lifting armmechanism.

The double-acting lifting ram 2 comprises a fixed piston 7 and a slidingcylinder 8, the latter at its lower end carrying a pin 9 constituting alower centre pivot of the lazy tongs mechanism 3, whereby any upwardmovement of the cylinder 8 gives rise to a magnified upward movement ofthe platform 5. The platform 5 also supports a bracket 10 to which ispivoted the lower part of a hydraulic tilting ram 11, having anextending piston rod 12.

Set round the lifting ram 2 are the various control valves describedmore particularly hereinafter in connection with the hydraulic/pneumaticcircuit diagram, together with separate pressurisable oil reservoirs 13and 14 for the tilting ram. These are all shielded within the skirt 6.

Referring now to FIGURES 3 and 4, a large bracket 15 mounted on platform5 provides a pivot at 16 at which is suspended a one-piece chair shell17. The shell carries a bracket 18 towards its foot end, at which thepiston rod 12 is pivoted, so that extension of the rod 12 will cause theshell 17 to swing about the pivot 16 in an anticlockwise direction asseen in FIGURE 3. The rearwardly tilted position of the shell is shownin FIGURE 3 in chain dotted outline. Sectional upholstery 19 is fittedto the shell 17. In the vicinity of the angles between the seat portionand leg-supporting portion of this upholstery, a plate 20 is hinged at21 to the shell 17, with its free forward end pointing towards the footof the shell. The bracket 15 carries a post 22 which protrudes through ahole in the shell 17 when the latter is rotated to its forwardly tiltedposition, to engage the plate 20, thereby preventing the plate fromcompleting its return movement to a fully forward position. Inconsequence, as shell 17 is swung from a backwardly tilted to a fullyforward position, that is, in a clockwise direction as seen in FIGURE 3,a point is reached where the plate 20, lying on the upper face of theshell 17 below the upholstery 19, is contacted by the post 22. Followingthis, continued rotation of the plate 20 to follow the shell 17 isprevented, and in consequence the portion 23 of the upholsteryimmediately over the plate 20 is lifted away from the shell 17. Thiscorresponds to an increase in the obtuse angle between the seat portionand leg portion of the upholstery 19, as the seat swings to a forwardlytilted or seated position or, conversely, to a diminution in this angleas the seat swings from a seated to a reclining position. In the latterposition, therefore, the patient is supported in a natural, restingposition with the lower part of the body comparatively straight while onbeing returned to an upright, seated position the angle at the knee isautomatically altered so that the knee becomes bent, which isappropriate to a seated position.

For the accommodation of a child, intermediate section 24 of theupholstery 19 is supported by a metal shell 25 hinged at 26 andassociated with struts 27, 28 and 29 which are pivoted together andnormally lie tucked in at the side of the upholstery as seen in FIGURE4. The shell 25 and the upholstery portion 24 can thus be swung up, asillustrated in chain dotted outline in FIGURE 3 and thereby serve as achilds seat. To lock the struts 28 and 29 it is arranged that the hinge30 therebetween permits only a limited rotation of the strut 29 in aclockwise direction relative to the strut 28. A recess 31 is provided inthe shell 17, in which the lower end of the strut 29 can seat when thehinge 30 has been pulled out (to the right) beyond the over-centreposition of the struts 28 and 29, so that downward pressure against asupporting bracket 32 carried by the hinge 30, exerted by the shell 25,holds the strut 29 locked in its position of maximum clockwise rotation.The struts 27 serve as arm supports for a child, whereas separate armsupports 33 are provided for the chair as a whole.

Referring now more particularly to the circuit diagram, FIGURE 5, thelifting ram is seen to be single-acting with its upward extensionpowered by the admission of hydraulic fluid under pressure in the space35 between the piston 7 and cylinder 8. The return movement is of courseeffected by gravity. The skirt 34 of the piston 7 is sealed by a plate36 at the bottom and serves as return reservoir for the hydraulic fluidin space 35.

Operation of the lifting and tilting mechanisms is initiated bypneumatic pilot valves 37, 38, 39 and 40 which serve respectively forthe movements raise, forward tilt, lower and backward tilt. These pilotvalves, which are all connected in parallel to a supply pipe 41 forcompressed air, have the same construction. Each comprises a poppetvalve member 42 which seals the compressed air from a central chamber 43until depressed against the action of a return spring 44. The chamber 43is occupied by a valve spool or bobbin 45 which is tubular at its innerend, serving in its rest position to connect the inner portion of thechamber with an exhaust port 46 situated towards the outer end of thechamber 43. A sealing ring 47 carried by the spool 45 preventscommunication between the inner part of the chamber 43 and the exhaustport 46 except by way of the tubular spool. The latter has an extension48 serving as a press button for actuating the valve, by inward movementof which the spool 45 is brought to bear against the poppet valve member42. Further inward movement depresses the valve member 42 and therebyadmits compressed air from pipe 41 to the inner part of the chamber 43;at the same time a sealing disc 49 obturates the normally open end ofthe tubular spool 45 thus shutting off connection to the exhaust port46. Upon release of button 48, air pressure acting on the inner part ofthe spool 45 returns the latter to its initial, resting position; thepressure differential across the valve member 42 resulting from chamber43 now being connected to exhaust, aided by the spring 44, presses thevalve member 42 to its closed position shown in the drawing. The innerpart of the chamber 43 of the valves 37, 38, 39 and 40 is connected toan air line 50, 51, 52 and 53 respectively. Each of these is thereforeconnected to exhaust when the respective button 48 is released, and tothe compressed air supply when the respective button is depressed.

Taking first the pilot valve 37, the pilot air line 50 leads to the mainair raise valve 54. This generally resembles the valve 37, having anexhaust port 55 correspending to the port 46, a tubular spool 56corresponding to the spool 45, and a poppet valve member 57 simi lar tothe valve member 42 carrying a sealing disc 58. The action of the valve54 is to connect a pipe 59 to the compressed air supply pipe 41 or toexhaust depending on the position of the spool 56, but in this case thelatter is moved by compressed air from line 50 acting on the head 60 ofthe spool. The pipe 59 leads to the air space 61 within the skirt 34,just below the piston 7, whilst a small branch line 62 leads to an oillock valve 63. This oil valve is inserted in an oil pipe 64 connectingthe hydraulic fluid in the space 35 with the space 65, serving as oilreservoir, within the piston skirt 34 below the air space 61. A poppetvalve member 66 controlling the movement of oil through the valve, isdepressed to open the valve 63 by the action of compressed air from thepilot air line 62, on a piston 67. The latter, which is detached fromthe valve member 66, has its own return spring 68. Thus, when valve 37is actuated, valve 54 is opened to admit compressed air to space 61 andmore or less instantaneously pressurise the hydraulic fluid in space 65.This operation of valve 54 results from the fact that the area of heador piston 60 is greater than the area of poppet valve member 57 andconsequently, even though poppet valve member 57 is normally held closedby pressure from air supply line 41, the force exerted by head or piston60 will be greater than that holding poppet valve member 57 closed andtherefore, upon depressing the button 48 of valve 37, the poppet valvemember 57 of valve 54 will be opened. At the same time the compressedair is fed along the pilot air line 62 and acting on the piston 67,automatically opens valve 63 so that the now pressurized hydraulic fluidcan flow into space 35, lifting the ram cylinder 8. As soon as therespective button 48 is released line 50 is connected to exhaust, sothat spool 56 in valve 54 moves to connect the air line 59, and hencespace 61 and line 62, to exhaust. Piston 67 moves under its returnspring 68, permitting valve member 66 to close under oil pressure andunder its own return spring 69. Closure of valve 63 locks the cylinder 8in position.

To lower the ram cylinder 8 and with it, the chair of FIGURES 3 and 4,the lower pilot valve 39 is actuated. This is connected by its pilot airline 52, only to the oil valve 63. To avoid cross connection with valve54 by way of the pilot air line 62, the air from line 52 is led to theback of a separate, free piston 7 which depresses oil valve member 66 bypushing piston 67. Since the air in space 61 is already connected toexhaust through valve 54, the hydraulic fluid in reservoir space 65 isat atmospheric pressure and the fluid in space 35 is expelled by gravityacting upon the supported dental chair. When button 48 of valve 39 isreleased this flow of hydraulic fluid is stopped by return movement ofvalve member 66 closing the oil valve 63, locking cylinder 8 inposition. A restriction such as a needle valve 71 may be inserted inline 52 to cushion the downward movement by slowing the opening andclosing of valve 63 by valve 39.

The double-acting hydraulic cylinder 11 is connected at one side of thepiston 72 by way of an oil pipe line 73 to a valve 74 and from there bya continuation of the oil line 73 to the oil reservoir 13. At the otherside of the piston 72, the cylinder 11 is connected by an oil line 75 toa valve 76 and from there by a continuation of the oil line 75, to thereservoir 14. For convenience, these two reservoirs are shown in FIGUREon their side. The valves 74 and 76, which are simple poppet valvesserving to close the respective oil line when released, are mounted sideby side for simultaneous actuation by a pneumatic ram 77. As in the caseof the oil valve 63, the pneumatic action of the ram 77 contains twoseparate pistons 78 and 79 arranged so that the ram can be operatedeither by compressed air supplied through the air line 80 behind thepiston 78, or by compressed air supplied through the air line 81 behindthe piston 7 9. In the latter case, the piston 79 will push the piston78 forwards, but the arrangement maintains a permanent air seal betweenthe lines 80 and 81. The line 81 is an extension of the line 51 frompilot valve 38, which supplies compressed air to the space 82 in the topof the oil reservoir 14, whilst the air line is an extension of the airline 53 which supplies compressed air to the space 83 in the top of theoil reservoir 13. In the resting state, when neither valve 38 nor valve40 is actuated, each of these pilot valves maintains the respectivelines 51, 81 and 53, 80 open to exhaust so that the hydraulic fluid onneither side of the piston 72 is pressurised, whilst each of the valves74, 76 is held shut under the influence of a respective return spring84, 85 to lock the position of the piston 72 by preventing movement ofhydraulic fluid to and from the reservoirs 13, 14. As soon as one of thepilot valves 38, 40 is actuated, the respective oil reservoir ispressurised by the admission of compressed air, whilst through theaction of the pneumatic ram 77 each of the valves 74 and 76 is openedthus permitting hydraulic fluid to flow from the pressurised reservoirto the respective side of the piston 72 and from the other side of thepiston 72, to the reservoir which is not pressurised and is stilltherefore open to exhaust through its respective pilot valve 38 or 40.

The arrangement according to the invention thus permits the use ofcomparatively simple valves affording the minimum of obstruction to theflow of hydraulic fluid, whilst keeping the various hydraulic andpneumatic circuits separate.

If desired, a further valve shown in dotted outline at 86 may beprovided in the pilot air line 50 arranged to close the connection tovalve 37, and open valve 54 above piston 60 to exhaust when tripped. Theresult will therefore be to arrest the upward movement of the liftingram, the valve 86 conveniently serving as a limiting valve forthemaximum height of the dental chair. Provision will in general be madefor positioning this valve so that it is tripped when a desired maximumextension of the lifting ram has been reached. It will be appreciatedthat, although the valves 74 and 76 are shown as being entirely separatevalves, actuated in unison, the respective valves for the two oilreservoirs can be constructed as parts of a double valve having forexample a single sliding spool or bobbin. It will also be appreciatedthat the pin 9 is duplicated as is the trellis mechanism 3 on each sideof the ram 2; likewise to maintain a proper balance, the

post 22 is duplicated and fitted one to each side of the bracket 15.

I claim:

A body support comprising a vertically movable ram mechanism, a chairpivotally mounted on a horizontal axis on said ram mechanism formovement between an upright and reclining position, a double actinghydraulic cylinder connected. to said chair for moving the same betweensaid positions, a pair of reservoirs for hydraulic fluid, one reservoirbeing connected to one end of said hydraulic cylinder and the otherreservoir being connected to the opposite end of said hydrauliccylinder, an on-otf valve in the connection between each reservoir andeach end of said hydraulic cylinder, pneumatic means for simultaneouslyopening said on-oif valves, spring means for closing said on-otf valves,an air pressure supply pipe, a control valve connecting said supply pipeto one reservoir and said pneumatic means, said control valve in oneposition serving to supply air pressure to said one reservoir andpneumatic means to force fluid into one end of said hydraulic cylinderwhile connecting said opposite end of said cylinder to said otherreservoir, and in another position to connect said one reservoir andpneumatic means to an exhaust, and a second control valve connectingsaid supply pipe to the other reservoir and said pneumatic means, saidsecond control valve in one position serving to supply air pressure tosaid other reservoir and pneumatic means to force fluid into theopposite end of said hydraulic cylinder while connecting said one end ofsaid cylinder to said one reservoir, and in another position to connectsaid other reservoir and pneumatic 7 8 means to an exhaust, wherebyoperation of said hydraulic 2,069,540 2/ 1937 Sanford 18079.2 cylinderin either direction is controlled by said first and 2,672,917 3/1954Collura 297327 second control valves. 3,025,108 3/1962 Teague 297--3303,112,676 12/1963 Boulsover. References Cited by the Examiner 5 UNITEDSTATES PATENTS FRANK B. SHERRY, Przmary Exammer. 1314,153 8/1919Schneidar ZUGEL, Assistant x miner. 1,596,909 8/1926 Weeks 297112

